#imageContainer {
    width: 100vw;
    height: 100vh;
    overflow: hidden;
    display: flex;
    justify-content: center;
    align-items: center;
    position: fixed;
    left: 0;
    top: 0;
    background: #a0a0a0;
    box-sizing: border-box;
    padding: 20px;
}

#imageContainer img {
    max-width: 100%;
    max-height: 100%;
    user-select: none;
    display: block;
}
.box{
    position: relative;
}

.btn{
    position: fixed;
    z-index: 3;
    left: 0;
    bottom: 10px;
    right: 0;
    margin: auto;
    width: 40px;
    height: 24px;
    background: #f0f0f0;
    border-radius: 4px;
    color: #5c5c5c;
    display: flex;
    justify-content: center;
    align-items: center;
    font-size: 12px;
}
.cvs{
    width: 100%;
    position: fixed;
    left: 0;
    top: 0;
    display: block;
    z-index: 3;
    box-shadow: 5px 5px 5px #5c5c5c;
}